This is a long term study looking at effect of early treatment in various urea cycle disorders. Survival of patients rescued from neonatal hyperammonemic coma argininosuccinase deficiency (n=22), 91.7%; (n=27). 87.1%, carbamyl phosphate synthetase and ornithine transcarbamylase deficiencies (n=38), 38%.Survival of patients (n=10) with deficiencies of carbamyl phosphate synthetase and ornithine transcarbamylase who were treated prospectively thereby preventing neonatal hyperammonemic coma is 78%.